The present invention relates to an integrated circuit having a synchronous circuit and an asynchronous circuit and to a method for operating such an integrated circuit.
Integrated circuits often have synchronously operated and asynchronously operated circuit sections which are connected to one another for data exchange, for example. In this case, in the synchronously operated circuit sections are clock-controlled, in other words there is generally a globally available clock signal present by means of which the operation of the synchronous circuit section is controlled time-synchronously. In contrast to this, an asynchronously operated circuit section is not clock-controlled. Integrated circuits constructed in this way are found for example in the field of memory circuits, such as for instance, in the field of so-called embedded DRAMs (Dynamic Random Access Memories). In this case, by way of example, a DRAM memory circuit which essentially operates asynchronously is contained in an integrated circuit which additionally has synchronous circuit sections.
If different circuits which operate synchronously with respect to a clock signal and asynchronously, respectively, are used in an integrated circuit, then it is necessary to provide defined interfaces between the different circuits concerned. Clock-controlled register circuits are usually used for this purpose. In this case, data from a synchronous circuit are stored in an input register circuit with, for example, the rising edge of the clock signal. The data are transferred from the input register circuit into the relevant asynchronous circuit, the data are processed in the asynchronous circuit and forwarded to an output register circuit, into which the data are accepted upon the next rising edge of the clock signal. The data of the output register are transferred to the synchronous circuit for further processing.
In this case, difficulties may occur in particular if the data processing duration of the asynchronous circuit is longer than the period duration of the clock signal. This is because the input data for the asynchronous circuit that are to be stored in the input register circuit can change with the next rising edge of the clock signal. For proper operation of the integrated circuit, the input data must remain the same throughout the processing time of the asynchronous circuit, in order to ensure correct processing by the asynchronous circuit. In order to hold the input data for a plurality of clock cycles, it is necessary, for example, to provide an additional register in the synchronous circuit.
If it is established in this case, for example, that the synchronous circuit further processes the data from the output register circuit only after a defined number of clock cycles, this can have the effect that the synchronous circuit has to wait for an unnecessarily long time for the processed data of the asynchronous circuit for further processing. This can occur primarily in the case of variable clock frequencies of the synchronous circuit and can limit the data throughput.
It is accordingly an object of the invention to provide an integrated circuit having a synchronous circuit and an asynchronous circuit, and a method of operating the integrated circuit which overcomes the above-mentioned disadvantages of the prior art apparatus and methods of this general type. In particular, it is an object of the invention to provide an integrated circuit which enables a relatively high data throughput between the synchronous circuit and the asynchronous circuit.
With the foregoing and other objects in view there is provided, in accordance with the invention, an integrated circuit, that includes: a synchronous circuit; an asynchronous circuit; an input register circuit connected to the synchronous circuit and the asynchronous circuit, the input register circuit having a terminal receiving a first control clock signal for controlling data transfer; an output register circuit connected to the synchronous circuit and the asynchronous circuit, the output register circuit having a terminal receiving a second control clock signal for controlling data transfer; and a sequence controller. The synchronous circuit stores data in the input register circuit so that the data can be processed in the asynchronous circuit. The asynchronous circuit stores the processed data in the output register circuit so that the processed data can be further processed in the synchronous circuit. The sequence controller is connected to the asynchronous circuit for generating the first control clock signal and the second control clock signal in dependence on a duration required for the data to be processed in the asynchronous circuit.
With the foregoing and other objects in view there is also provided, in accordance with the invention, a method for operating the inventive integrated circuit, in which the first control clock signal is activated for the purpose of transferring data from the synchronous circuit into the input register circuit, the data are transferred from the input register circuit into the asynchronous circuit and are processed in the asynchronous circuit, the first control clock signal is inactivated by the sequence controller within the data processing duration of the asynchronous circuit, and in which the second control clock signal, at or after the end of the data processing duration of the asynchronous circuit, triggers transfer of the processed data into the output register circuit.
The integrated circuit and the operating method enable a comparatively high data throughput between the synchronous circuit and the asynchronous circuit. The data exchange between the asynchronous circuit and the synchronous circuit is adapted to the processing speed of the asynchronous circuit. This means, for example, that the synchronous circuit does not have to wait for a previously defined number of clock cycles for the result of the asynchronous circuit, which lowers the data throughput.
The fact that the first control clock signal is deactivated within the data processing duration of the asynchronous circuit avoids the situation in which data stored in the input register circuit are overwritten by new data of the synchronous circuit, as long as the asynchronous circuit has not yet concluded the processing of the old data. The fact that the second control clock signal, at or after the end of the data processing duration, triggers the transfer of the processed data into the output register circuit enables the further processing of the data to be carried out by the synchronous circuit immediately after the end of the processing in the asynchronous circuit. Besides the relatively high data throughput, in addition, a relatively simple design of the integrated circuit is made possible since there is no need for additional registers or circuits for holding or buffer-storing the input data.
In accordance with an added feature of the invention, the integrated circuit has a terminal for a clock signal, the terminal for the clock signal and the terminal for the first control clock signal are connected to one another via a controllable switching means. For generation of the first control clock signal, the controllable switching means can be controlled by the sequence controller. If the switching means is closed, then the clock signal forms the first control clock signal. If the switching means is open, then the first control clock signal is switched off or deactivated. This means that the integrated circuit itself switches off the first control clock signal by means of the sequence controller, in order to hold the data stored in the input register circuit, in order that the asynchronous circuit can carry out the data processing properly. The integrated circuit additionally determines, by means of the sequence controller, the instant that the data is output from the asynchronous circuit and the renewed switch-on of the first control clock signal.
Such a mode of operation of the integrated circuit is particularly advantageous for the case where the terminal for the clock signal is connected to the synchronous circuit for the purpose of controlling the operation of the synchronous circuit, and, in addition, the clock frequency of the clock signal is adjustable in a variable manner. A high data throughput is ensured in this case even in the event of an altered clock frequency of the clock signal and thus in the event of an altered data processing speed of the synchronous circuit. A comparatively slowly clocked design of the synchronous circuit can accept the data, for example, as early as after two clock periods, and a comparatively fast design of the synchronous circuit must wait for correspondingly more clock periods in order to accept the result of the asynchronous circuit. As a result, the data transfer between the synchronous circuit and the asynchronous circuit is adapted to the processing speed of the asynchronous circuit even in the event of an altered clock frequency of the clock signal, whereby a high data throughput is always achieved.
The invention can be used for diverse kinds of integrated circuits. By way of example, the asynchronous circuit has a memory circuit of the DRAM type. A comparatively high memory throughput is made possible with such a so-called embedded DRAM design. In addition, the integrated circuit can be used for the case where the asynchronous circuit has an analog/digital converter, for example.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an integrated circuit having a synchronous and an asynchronous circuit and method for operating such an integrated circuit, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.